BRPI0707492A2 - cutting insert - Google Patents

Abstract

CUTTING INSERT. A cutting insert (20) for a machine tool comprising a flat blade formed of polycrystalline diamond material and having a front face (21) in the same form as the PCD phase (23) with at least one cutting edge (22) in it and a rear face formed from the second stage substrate 24, the rear face having serrations (25) in the same formed inside the second stage substrate (24), preferably substantially normal to each cutting edge.

Description

Report of the Invention Patent for "INSERT DECORTE".

Technical Field

The invention relates to cutting inserts for machine tools such as mandrels and drills and to a process of attaching a cutting insert to a machine tool.

Diamond is the hardest and therefore the toughest of all abrasion materials and some sharp edges or blade edges for machine tools are formed from diamond powder which can be formed from polycrystalline diamond (PCD) which is extremely hard and It has good abrasion resistance when compared to carbide cutting tools.

PCD is a composite of individual diamond crystals sintered together in an interconnected network. PCD crystals can be directly sintered into a cutting tool such as a rotary cutter as shown in European Patent 0528243A.

PCD is also available in round raw materials comprising a first phase of PCD formed from a second phase of sintered tungsten carbide. The raw materials are made by applying ultra-high pressure and high temperature to a layer of diamond dust on a metal carbide bed, nitrite or carbonitride powder substrate. The second metallic phase of the cemented carbide substrate infiltrates the interstitial regions between the diamond crystals during the process and binds the diamonds together. The resulting crude material combines an extremely hard PCD surface bonded to a carbide substrate. All of this is described in German Patent 2408735-A.

PCD raw materials are very expensive and the PCD raw material is then typically cut into a number of small portions that can be assembled directly to the cutting tools by strong welding as shown in German Patent 19937739-A. However, this has a disadvantage that the entire tool must be discarded or once serviced at the factory, the tip of the PCD tool becomes worn or damaged.

Another disadvantage of the raw PCD material is that the material is relatively fragile and can rupture if subjected to tool clamping loads. In another development, a PCD tool tip is welded or brazed to a support body which in turn is mechanically secured to a tool head. This arrangement ensures that any securing loads are taken up by the insert body and also permits the insertion of the insert. Such an insert is available from the requesting present.

Another known insert is shown in German Patent No. 4,423,861 which describes a cutting insert having PCD tips attached by strong welds against a body and which is reorientable in the tool allowing each tip to be used in turn.

Molding or welding to the edges of the PCD in a supporting body is an expensive operation and the tips must be precisely ground after the welding process.

Purpose of the Present Invention

The present invention seeks to provide a more cost-effectively manufactured and improved PCD cutting insert for a machine tool.

Description of the Invention

According to the invention, there is provided a cutting insert for a machine tool comprising a flat blade forming a polycrystalline diamond material and having a PCD phase formed front face with at least one cutting edge therein and a substrate formed rear face second stage and a rear face having only one minus one groove that normally extends to each cutting edge, the groove being formed within the second stage substrate.

Preferably, the groove is one of a plurality of knurls formed on the substrate.

The blade may have between two and four cutting edges and is preferably square or substantially square, preferably having four cutting edges and the rear portion of the blade is provided with two intersecting serrated assemblies.

Knurls can take many different shapes including symmetrical waveforms such as winding waves, zigzag shapes, corrugations and non-symmetrical knurls.

Also according to the invention there is provided a cutting tool comprising a body having a recess therein with a blade, according to a first aspect of the invention, mounted therein, each rear section groove of the blade interlocks with the shoulder or shoulders. cooperating on the tool to hold the blade against the machining loads.

Preferably, the shoulders extend across the overall width of the blade and the cutting blade is positioned adjustable to the shoulder (s) by a single screw threaded adjuster. interengage prevent the blade from oscillating during adjustment.

The projections in the tool may be formed as a serrated series and the serrations in the tool may be formed in a recessed face or alternatively on a removable carrier which is mounted in the recess.

The blade is secured to said face by the head of a set screw or a clamping plate. However, the clamping load can be relatively low since machining loads are taken up by the intercoating grooves (s) and shoulder (s).

With a square blade, having rear-facing serrated assemblies, each of the four cutting edges can be used by loosening the blade to release the interlocking serrations and then turning the blade as desired and reengaging the serrations.

A method of attaching a dicing blade of PCD material to a cutting tool is further provided, the cutting blade having at least one cutting edge formed on the PCD face of the blade, wherein the cutting blade is provided with at least one groove formed. in the second stage PCD substrate on its rear face and the cutting blade is fixed against a mutually interengageable shoulder provided in the tool.

Preferably, groove (s) are provided substantially normal at each cutting edge, with the blade cutting edge being adjusted to a new position by movement of the blade along a shoulder or shoulders provided on the blade. tool.

If the blade has a plurality of cutting edges, the blade edge may be changed or the blade changed simply by removing the conveyor blade and relocating said blade or another identical blade into the knurls or shoulders to provide a new cutting edge. with mutually interengating grooves and cams ensuring the realignment of said cutting edge.

Figure 1 - It is a plan view of a cutting insert of the previous technique,

Figure 2 is an isometric view of a cutting insert according to the present invention.

Figure 3 is an end view of the cutting insert shown in Figure 2,

Figure 4 - A plan view of the cutting blade of Figure 2 showing the PCD surface.

Figure 5 - A schematic radial section through a cutting tool showing the cutting insert in situ, Figure 6 - A side view of the tool shown in Figure 5.

Detailed Description of the Invention

A prior art blade or cutting insert 10 is shown in Figure 1 and has a substantially rectangular tungsten carbide body 11 in plant. The front face 14 of the insert has a depression 15 or dimple formed therein which is located symmetrically around the approximately half-length centerline and the half-width centerline of the face 14. Depression is used to fix the insert IO in a tool as described in detail in German Patent 2338196.

A PCD cutting tip 12 is bonded to a weld 13 formed in the tungsten carbide body 11.

Referring next to Figures 2 to 4 in particular, an insert or cutting blade 20 according to the present invention is shown. The insert 20 is cut from a raw PCD material having a PCD23 phase formed on a carbide substrate 24 using a electrode discharge wire cutting process. The insert 20 is of a substantially square planar shape having a flat front face 21 in the PCD phase with at least two and preferably four cutting edges 22 formed therein. The PCD phase generally has a thickness of 0.45 - 0.7 mm depending on the size of the diamond grains. Carbide substrate 24 forms the rear portion of insert 20 and is typically between 0.55 - 2.6mm in thickness. For the present embodiment, the PCD phase 23 is about 0.7mm in thickness and the carbide substrate is between 1.3 and 2.6mm in thickness.

The rear portion of the insert 20 is provided with at least one groove 25 on the rear surface and preferably with a plurality of serrations 35 thereon. The knurls 25 comprise knurls that extend substantially normal to the cutting edges 24 to the full extent of the blade 16. In the present four-edged blade example 34, a set of knurls 25A extends transversely of the other set of knives 25B of so that the knurls 25A and 25B intersect each other forming separate pyramidal projections. The serrations typically have a depth of 0.85mm and are ground into the substrate by means of a diamond grinding wheel formed and located entirely within the second carbide phase substrate 24.

With two sharp edges on opposite sides of the blade, the knurls 25 extend only between said opposite sides.

Referring to Figures 5 and 6 of the drawings, a tool 51 is shown having a shaft 52 which in use is fixed to a tool for rotating the tool about its longitudinal axis. Tool 51, which is typically a mandrel , has a cylindrical head 53 carrying at least one cutting insert 20. Head 53 is typically provided with a plurality of angularly spaced cutting inserts 20 around the head 13, and only one of which is shown for simplicity. and the invention will be described in detail with reference to said one blade only, any other blade being substantially identical.

Each insert 20 is disposed in a respective recess 54 located on the periphery of the head 53. The head 53 may also have a plurality of centering pads (not shown) extending axially spaced around the head. If two inserts 20 are used, they may be diametrically opposed to one another.

Cutting insert 20 is radially oriented from head 53. Process 54 has a radial side face 56 against which a cutting insert is secured by a set screw 57.

The knurls 25 in the rear portion of the insert interengage with similar radial knurls 55 in the radial side face 56 of the recess 54. In this example, the knurls 25 and 55 are in the form of straight edges with triangular cross-section with the angle included in the apex. 45 - 909 arc, preferably around 609 arc. Chamfers have a pitch between 1.00mm and 1.75mm and the chamfered tops are chamfered. An axially extending clearing hole 58 is provided at the intersection of the side face 56 of the recess 54 and the radially inner side of the recess.

The insert 20 is retained in the recess by the screw 57 which presses the insert 20 so that the knurls 25 and 55 are securely retained interlocking so that any loads on the blade are transmitted to the tool head 53 through the interengaged knurls.

The inwardly facing side of the insert is fitted with at least one adjuster 59. Each adjuster 59 comprises a wedge wedge which is movable in a cordal hole 63 by means of an adjuster screw 64 for radial adjustment of the insert. cutting edge height 22. The total adjustment range will be around 0.5mm.

When an insert is first fitted to a tool, the insert is adjusted to a correct radial adjustment by trial and error technique by adjusting the position of the insert. The blade is typically adjusted to an accuracy of 3-5 microns. Next, if it is desired to renew the cutting edge 22, the insert 20 is removed from the notch 22 by unscrewing the retaining screw 57. The insert 20 is then repositioned to provide a new edge or replaced with a new identical blade. Since the tabs 25 on the rear face of any blade are precisely connected to the cutting edge (s), the new blade when adjusted on the mandrel will provide a precisely positioned cutting edge so it needs to be only radially adjusted.

The insert 20 may be mounted on a removable carrier (not shown) and the insert 20 and the carrier are secured to the respective recess 54.

Typical machine tools in which the inserts 20 may be used are drills, mandrels, grinding heads, etc.

Claims (12)

1. A cutting insert for a machine tool comprising a flat blade formed of polycrystalline diamond material and having a front face formed therefrom of the PCD phase with at least one cutting edge thereon and a rear face formed of the second substrate. stage, the rear face there having at least one groove formed within the second stage substrates. An insert according to claim 1, wherein at least one groove is provided on the rear face substantially normal to each cutting edge. An insert according to claim 1 or claim 2, wherein each groove is one of a plurality of serrations formed in the substrate. An insert according to any one of claims 1 to 3, wherein the insert has two to four cutting edges. An insert according to claim 4, wherein the insert is substantially square with four cutting edges and the blade rear portion is provided with two sets of intersecting serrations. A cutting tool comprising a body having a recess therein with an insert as defined in any one of claims 1 to 5, mounted therein and each groove in the rear portion of the insert mutually interengaging with a shoulder or shoulders. cooperating on the tool to secure the insert against machining loads. A cutting tool according to claim 6, wherein the cutting blade is adjustablely located along the shoulder by means of a single screw threaded adjuster. A cutting tool according to claim 6 or claim 7, wherein the insert is mounted within a recess in the circumferential surface of the tool and any cams or lugs are provided by knurls on a side face of the tool. recess. The cutting tool of claim 8, wherein the insert is secured to said face by the head of a set screw or a set plate. 10. Method of attaching a PCD material cutting blade In a cutting tool, the cutting blade having at least one gum cutter formed on the PCD face of the blade, wherein the cutting blade is provided with at least one groove within the second phase substrate. and the blade is fixed against an interengageable shoulder or cam provided in the tool, so that the groove (s) and cam (s) are mutually interengaged. The method of claim 10, wherein said at least one groove extends substantially normal with the cutting edge of the blade for the full width of the blade and the blade is adjustablely mounted on the shoulder or by the movement of the blade along the rebound (s)) by the adjusting means provided in the tool. A method according to claim 10 for attaching a cutting blade having a plurality of cutting edges, wherein the blade knife may be changed or the blade simply changed by removing the tool blade and relocating said blade or another identical blade. at the shoulder (s), to provide a new cutting edge, with the shoulder (s) and shoulder (s) mutually interengaging, ensuring re-alignment of said cutting edge.